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- ItemDigital Electrochemistry for On-Chip Heterogeneous Material Integration(Weinheim : Wiley-VCH, 2021) Bao, Bin; Rivkin, Boris; Akbar, Farzin; Karnaushenko, Dmitriy D.; Bandari, Vineeth Kumar; Teuerle, Laura; Becker, Christian; Baunack, Stefan; Karnaushenko, Daniil; Schmidt, Oliver G.Many modern electronic applications rely on functional units arranged in an active-matrix integrated on a single chip. The active-matrix allows numerous identical device pixels to be addressed within a single system. However, next-generation electronics requires heterogeneous integration of dissimilar devices, where sensors, actuators, and display pixels sense and interact with the local environment. Heterogeneous material integration allows the reduction of size, increase of functionality, and enhancement of performance; however, it is challenging since front-end fabrication technologies in microelectronics put extremely high demands on materials, fabrication protocols, and processing environments. To overcome the obstacle in heterogeneous material integration, digital electrochemistry is explored here, which site-selectively carries out electrochemical processes to deposit and address electroactive materials within the pixel array. More specifically, an amorphous indium-gallium-zinc oxide (a-IGZO) thin-film-transistor (TFT) active-matrix is used to address pixels within the matrix and locally control electrochemical reactions for material growth and actuation. The digital electrochemistry procedure is studied in-depth by using polypyrrole (PPy) as a model material. Active-matrix-driven multicolored electrochromic patterns and actuator arrays are fabricated to demonstrate the capabilities of this approach for material integration. The approach can be extended to a broad range of materials and structures, opening up a new path for advanced heterogeneous microsystem integration.
- ItemShape-Controlled Flexible Microelectronics Facilitated by Integrated Sensors and Conductive Polymer Actuators(Weinheim : Wiley-VCH Verlag GmbH & Co. KGaA, 2021) Rivkin, Boris; Becker, Christian; Akbar, Farzin; Ravishankar, Rachappa; Karnaushenko, Dmitriy; Naumann, Ronald; Mirhajivarzaneh, Aaleh; Medina-Sánchez, Mariana; Karnaushenko, Daniil; Schmidt, Oliver G.The next generation of biomedical tools requires reshapeable electronics to closely interface with biological tissues. This will offer unique mechanical properties and the ability to conform to irregular geometries while being robust and lightweight. Such devices can be achieved with soft materials and thin-film structures that are able to reshape on demand. However, reshaping at the submillimeter scale remains a challenging task. Herein, shape-controlled microscale devices are demonstrated that integrate electronic sensors and electroactive polymer actuators. The fast and biocompatible actuators are capable of actively reshaping the device into flat or curved geometries. The curvature and position of the devices are monitored with strain or magnetic sensors. The sensor signals are used in a closed feedback loop to control the actuators. The devices are wafer-scale microfabricated resulting in multiple functional units capable of grasping, holding, and releasing biological tissues, as demonstrated with a neuronal bundle.
- ItemA new dimension for magnetosensitive e-skins: active matrix integrated micro-origami sensor arrays([London] : Nature Publishing Group UK, 2022) Becker, Christian; Bao, Bin; Karnaushenko, Dmitriy D.; Bandari, Vineeth Kumar; Rivkin, Boris; Li, Zhe; Faghih, Maryam; Karnaushenko, Daniil; Schmidt, Oliver G.Magnetic sensors are widely used in our daily life for assessing the position and orientation of objects. Recently, the magnetic sensing modality has been introduced to electronic skins (e-skins), enabling remote perception of moving objects. However, the integration density of magnetic sensors is limited and the vector properties of the magnetic field cannot be fully explored since the sensors can only perceive field components in one or two dimensions. Here, we report an approach to fabricate high-density integrated active matrix magnetic sensor with three-dimensional (3D) magnetic vector field sensing capability. The 3D magnetic sensor is composed of an array of self-assembled micro-origami cubic architectures with biased anisotropic magnetoresistance (AMR) sensors manufactured in a wafer-scale process. Integrating the 3D magnetic sensors into an e-skin with embedded magnetic hairs enables real-time multidirectional tactile perception. We demonstrate a versatile approach for the fabrication of active matrix integrated 3D sensor arrays using micro-origami and pave the way for new electronic devices relying on the autonomous rearrangement of functional elements in space.
- ItemSelf-sufficient self-oscillating microsystem driven by low power at low Reynolds numbers(Washington, DC [u.a.] : American Association for the Advancement of Science, 2021) Akbar, Farzin; Rivkin, Boris; Aziz, Azaam; Becker, Christian; Karnaushenko, Dmitriy D.; Medina-Sánchez, Mariana; Karnaushenko, Daniil; Schmidt, Oliver G.Oscillations at several hertz are a key feature of dynamic behavior of various biological entities, such as the pulsating heart, firing neurons, or the sperm-beating flagellum. Inspired by nature’s fundamental self-oscillations, we use electroactive polymer microactuators and three-dimensional microswitches to create a synthetic electromechanical parametric relaxation oscillator (EMPRO) that relies on the shape change of micropatterned polypyrrole and generates a rhythmic motion at biologically relevant stroke frequencies of up to ~95 Hz. We incorporate an Ag-Mg electrochemical battery into the EMPRO for autonomous operation in a nontoxic environment. Such a self-sufficient self-oscillating microsystem offers new opportunities for artificial life at low Reynolds numbers by, for instance, mimicking and replacing nature’s propulsion and pumping units.
- ItemA Patternable and In Situ Formed Polymeric Zinc Blanket for a Reversible Zinc Anode in a Skin-Mountable Microbattery(Weinheim : Wiley-VCH, 2021) Zhu, Minshen; Hu, Junping; Lu, Qiongqiong; Dong, Haiyun; Karnaushenko, Dmitriy D.; Becker, Christian; Karnaushenko, Daniil; Li, Yang; Tang, Hongmei; Qu, Zhe; Ge, Jin; Schmidt, Oliver G.Owing to their high safety and reversibility, aqueous microbatteries using zinc anodes and an acid electrolyte have emerged as promising candidates for wearable electronics. However, a critical limitation that prevents implementing zinc chemistry at the microscale lies in its spontaneous corrosion in an acidic electrolyte that causes a capacity loss of 40% after a ten-hour rest. Widespread anti-corrosion techniques, such as polymer coating, often retard the kinetics of zinc plating/stripping and lack spatial control at the microscale. Here, a polyimide coating that resolves this dilemma is reported. The coating prevents corrosion and hence reduces the capacity loss of a standby microbattery to 10%. The coordination of carbonyl oxygen in the polyimide with zinc ions builds up over cycling, creating a zinc blanket that minimizes the concentration gradient through the electrode/electrolyte interface and thus allows for fast kinetics and low plating/stripping overpotential. The polyimide's patternable feature energizes microbatteries in both aqueous and hydrogel electrolytes, delivering a supercapacitor-level rate performance and 400 stable cycles in the hydrogel electrolyte. Moreover, the microbattery is able to be attached to human skin and offers strong resistance to deformations, splashing, and external shock. The skin-mountable microbattery demonstrates an excellent combination of anti-corrosion, reversibility, and durability in wearables. © 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH
- ItemSelf-assembly as a tool to study microscale curvature and strain-dependent magnetic properties(London : Springer Nature, 2022) Singh, Balram; Otálora, Jorge. A.; Kang, Tong H.; Soldatov, Ivan; Karnaushenko, Dmitriy D.; Becker, Christian; Schäfer, Rudolf; Karnaushenko, Daniil; Neu, Volker; Schmidt, Oliver G.The extension of 2D ferromagnetic structures into 3D curved geometry enables to tune its magnetic properties such as uniaxial magnetic anisotropy. Tuning the anisotropy with strain and curvature has become a promising ingredient in modern electronics, such as flexible and stretchable magnetoelectronic devices, impedance-based field sensors, and strain gauges, however, has been limited to extended thin films and to only moderate bending. By applying a self-assembly rolling technique using a polymeric platform, we provide a template that allows homogeneous and controlled bending of a functional layer adhered to it, irrespective of its shape and size. This is an intriguing possibility to tailor the sign and magnitude of the surface strain of integrated, micron-sized devices. In this article, the impact of strain and curvature on the magnetic ground state and anisotropy is quantified for thin-film Permalloy micro-scale structures, fabricated on the surface of the tubular architectures, using solely electrical measurements.